Solutions

1. Solutions

2. Bellringer Why is the last of the 4 laws of thermodynamics #3?

3. Topic #: Mixtures Element: All atoms with the same number of protons Compound: Groups of atoms that have reacted with each other

4. Mixture Collections of elements or compounds that have (at least not yet!) reacted with each other Gasoline and oxygen form a mixture, but these can also react with each other, given enough activation energy!

5. Types of mixtures Homogeneous: The same throughout in all parts Example Air Homogenized milk Heterogeneous: Different concentrations in different places Example Concrete Dirt

6. Solutions Homogeneous mixtures Solid, liquid, or gas Composed of: A solute that dissolves And a solvent that dissolves it

7. Solutions by solvent type: Aqueous: water is the solvent Example: Tea, sodas Tincture: alcohol is the solvent Example: Tincture of iodine

8. Alloys Solid solutions A metal is the solvent Mix when heated until the metal is liquid

9. Alloys with metals for both solvent and solute: Brass: 90% copper and 10% zinc Sterling silver: 92.5% Ag and 7.5% Cu 12 K Gold: 50% Au and 50% Cu

10. Alloys with a metal and metalloid Bronze: 90% copper and 10% tin Pewter: 10% copper and 90% tin Steel: 97% iron and 3% carbon

11. Amalgam An alloy of mercury Such as dental fillings

12. Bellringer Is a solution a mixture? Why or why not?

13. Topic #24: Solubility How well a solute dissolves in a solvent Generally expressed by Ksp

14. Factors affecting solubility

15. 1. Similarity Like dissolves like Polar solvents dissolve in polar solutes Non-polar solvents dissolve in non-polar solutes Polars and non-polars do not mix well If you try, they will separate with time.

16. Terms: Miscible: mixable, because they are similar Immiscible: not mixable, because they are not similar Polar: having charges, as ions (such as salt) or shape (such as water); the charges help pull particles apart. Non-polar: not having any charges (such as oil)

17. 2. Temperature Many solution processes are endothermic, they take energy. Adding heat helps solvents dissolve solid solutes. The reverse is true when gases are to be dissolved in solvents! (Gases move more with heat.)

18. 3. Pressure Drives gases into liquid solvents. Not much effect with liquids and solids.

19. Factors affecting the rate of solution: How can we make a solute dissolve faster?

20. 1. Particle size If the solute is ground very small, the solvent can get to more surface are and interact more. Which dissolves faster, granulated sugar or sugar cubes?

21. 2. Stirring Stirring brings fresh solvent in contact with the solute.

22. 3. Amount of solute already dissolved Fresh solvent can dissolve a solute faster. The more solute is in the solvent, the slower the solvent will dissolve the next amount. The first amount of solute dissolves rapidly; the later ones take longer.

23. 4. Temperature For solid and liquid solutes: Warmer solvent works faster. In which will a teaspoon of sugar dissolve faster: Hot tea or cold tea?

24. But for gases: Cold solvents dissolve more gases. Examples: Sodas lose their carbon dioxide as they warm up (�go flat�) Fish in summer go to deeper holes where the water is colder and holds more oxygen

25. Bellringer How salty can water become?

26. Topic #25 Relative strengths of solutions

27. Dilute Only a �little� solute in a solvent

28. Concentrated Has more solute in the solvent than dilute Need to be compared to have any meaning

29. Saturated The solvent holds as much solute as it possibly can under the stated conditions (Whatever they may be.)

30. Equilibrium (of saturated solutions) The solute is in equilibrium Some particles may be dropping out of solution, but others go in

31. Making a saturated solution Add an EXCESS of solute to the solvent. Mix. Let stand several hours. The presence of solid solute on the bottom indicates the liquid above it is saturated.

32. Conditions for saturation may change A hotter solvent can hold more solid or liquid solute A colder solvent can hold more gaseous solute Changing the ionic nature of the solvent or its pH can affect how much solute it holds

33. Supersaturated The solution holds more solvent than it should under current conditions

34. How is a supersaturated solution possible? The solvent dissolves a large quantity under other conditions The conditions change The solute remains in solution, temporarily!

35. Supersaturated sugar and crystals A large quantity of sugar is dissolved in hot water. The water cools down below the point it can contain that much sugar. The sugar stays in solution! Until a vibration or disturbance causes it to precipitate (fall out) Large sugar crystals (rock candy) form instantly on any rough surface (like string)

36. Unsaturated A solution having less solute than a saturated one. It may be dilute or concentrated.

37. Bellringer What happens to a car with no antifreeze?

38. Topic #26 Colligative Properties of water What solutes do to water just by being there Any solute will do these things Solute characteristics do not count Only quantity matters

39. Freezing point depression Solutes lower the freezing point of the solution below 0�C Solutes interfere with the formation of crystals Antifreeze keeps the car�s radiator fluids from freezing during cold weather.

40. Boiling point elevation Solutes hold onto water molecules that try to leave the surface This raises the boiling point of an aqueous solution above 100�C. Antifreeze also works to prevent the radiator fluids from boiling (and forming gases that can expand and push things apart)

41. Vapor pressure depression Just like with boiling, the solute particles interfere with water molecules leaving the surface. Fewer water molecules leaving means less vapor, and less pressure, above it.

42. Osmotic pressure increase Water will move through a semi-permeable membrane to the volume of greater concentration. This causes the volume with the greater concentration of solute to have greater osmotic pressure. Semi-permeable: Water can move through, but not bigger molecules (or sometimes charged ions)

43. Dialysis Waste from blood build up Saline solution introduced near body fluids Wastes move into saline, which is then removed

44. Saline and the body Hypertonic: Solution is more concentrated than cells. Cells shrivel as water leaves. Isotonic: Saline is equal to cells. (Ringer�s Solution.) Hypotonic: Cells are more concentrated than solution. Water moves into cells, making them swell, maybe to explode.

45. Effects of Osmotic Pressure

46. Bellringer Find the gram formula mass of NaCl:

47. Topic #27: Molarity Quantification Puts a number to concentration

48. Equation Molarity=Moles/Liters �Moles� will be moles of solute �Liters� will be total liters of solution

49. Mole calculations Moles=Mass (grams)/Gram Formula Mass Gram Formula Mass is calculated from the formula Example: NaOH

50. Example Problems Find the molarity of 80 g NaOH dissolved in water to make ten liters of solution:

51. Example: How much NaCl needs to be used to make 2 liters of 2M saline solution?

52. Example: 73 g of HCl will yield how many liters of a 0.1 M solution?

53. Bellringer In a solution of alcohol and water, which is the solvent and which the solute?

54. Topic #28: Dilutions Solvent can be added to a solution to make it less concentrated

55. Solute remains constant Only solvent is added Moles of solute is constant, even if more dilute Moles of solute = Molarity x Volume For any dilution of a solution

56. Equation M1 x V1 = M2 x V2 M1 : Starting molarity V1 : Starting volume M2 : Final molarity V2 : Final volume

57. Example 100 mL of a 0.2 M NaCl solution is diluted to one liter. What is its final concentration?

58. Example: You need 800 mL of 0.1 M HCl. How much from a 3M HCl stock solution do you need?

59. Serial Dilutions Based on factors of ten One part of a solution is added to nine parts solvent (water, growth medium, or saline) Used to dilute bacterial and other cultures

60. Serial dilution is used to count bacteria

61. Example: Count the bacteria in 2 L of nutrient broth 1 mL of broth is diluted into 9 mL media; this serial dilution is done six times. One mL of the final dilution is swabbed onto a Petri dish, and 15 colonies result. How many were in the original culture?

62. Bellringer Which adds more particles to a solution: Sugar or Salt (NaCl)?

63. Topic #29 Other methods of expressing concentration

64. Molality Moles of solute per kilogram of SOLVENT Usually a little more than molarity Used to calculate effects of colligative properties

65. Normality Used for acids and bases Not all these react equally Some have more reactive units Compares relative reactive strengths Abbreviated N

66. Calculations For acids, multiply the subscript of the hydrogen to the molarity For bases, multiply the subscript of the hydroxide to the molarity

67. Examples Find the normality of 0.3 M HCl Find the normality of 0.25 M H2SO4

68. Example Find the normality of 0.5 M NaOH Find the normality of 0.4 M Ca(OH)2

69. Percentage Concentration Two methods: One for liquid solutes Another for solid solutes

70. Volume/Volume Percentage mL solute per 100 mL solution Used for liquid solutes Example: 20 mL of alcohol are diluted to 50 mL with water. Find the % concentration:

71. Mass/Volume Percentage For solid solutes Grams of solute per 100 mL solution (Based on 1 mL of water being 1 gram in mass) Example: Find the concentration of 16 g NaCl diluted with water to 200mL.

72. Interconversions Example: Find the molarity of a 5% NaCl solution:

73. Bellringer: If heat is put into water to make it boil, where does the heat go when the water condenses back to a liquid?

74. Topic #30: Energy and State Energy has to enter or leave matter for it to change among solid liquid, and gas phases

75. GAS LIQUID SOLID

76. Law of Conservation of Energy Heat of Condensation = Heat of Vaporization Heat of Crystallization = Heat of Fusion

77. Cooling effects Both evaporation and boiling cool a liquid Boiling happens throughout a liquid Boiling water cannot normally be hotter than 100�C due to this cooling Evaporation happens only on the surface and at any temperature, but it still cools!

78. Higher pressure above a liquid will raise its boiling point. Pressure cookers run at over 100�C With no atmospheric pressure, water on the moon�s surface boils away at any temperature

79. Liquefaction Under enough pressure, any gas becomes a liquid. Nitrogen, oxygen, and several inert gases are extracted from the air this way. Critical temperature: Maximum temperature at which liquefaction works. Critical pressure: Required pressure for liquefaction at critical temperature.

80. Changing pressure changes boiling and melting points: Phase diagram

81. Distillation Used to separate materials by boiling point Liquid ? Gas ? Liquid

82. Bellringer Which is your favorite color? Why? Which is opposite blue on the color wheel?

83. Topic #31: Coordinate Chemistry Looks at small molecules that interact with larger electron orbitals

84. Hydrates Water is attached to the molecule without reacting Typically forms colorful crystals Water is written last in the formula

85. Example Cupric sulfate pentahydrate CuSO4�5 H2O Bright blue crystals Anhydrous form, CuSO4, is a white powder.